1. Field of the Invention
The present invention relates to a hard disk drive (HDD). More particularly, the present invention relates to the suspension assembly of an HDD which supports the read/write head.
2. Description of the Related Art
Hard disk drives (HDDs), which are used by computers to store information, read data recorded on a disk or write data onto the disk using a read/write head. Such HDDs include an actuator for positioning the read/write head over the disk and a suspension assembly. The read/write head is mounted to the suspension assembly and the suspension assembly is attached to a front end of the actuator.
Referring to FIG. 1, a conventional suspension assembly 40 includes a load beam 41, a bracket 43 having a flexure and attached to the load beam 41, a slider 49 mounted to the bracket 43, and a stopper 50. The front end of the load beam 41 forms a lift tab 47, and an intermediate part of the load beam 41 forms a dimple 45 projecting towards the bracket 43. The load beam 41 and the bracket 43 contact each other through the dimple 45. A read/write head of the HDD (not shown) is attached to the slider 49. The read/write head reads data recorded on a disk 20 or writes data onto the disk 20. The slider 49 is a negative pressure type slider, which means that both positive and negative air bearing pressure arises on different parts of an air bearing surface of the slider during its flight over the disk 20.
The disk 20 rotates at a high speed while the read/write head is reading/writing data. Air that is induced to flow between the disk 20 and the slider 49 generates a lift force on the suspension assembly 40. As a result, the read/write head attached to the slider 49 writes or reads data while hovering at a predetermined height above the disk 20. At this time, the dimple 45 allows the slider 49 to roll and pitch to a limited extent. When the HDD is turned off and the disk 20 stops rotating, the slider 49 is moved off of the disk 20 (unloading operation) and the lift tab 47 at the front end of the load beam 41 is moved along and then parked on a parking ramp (not shown) so that the slider 49 is stable.
The lift tab 47 is moved by the parking ramp in a direction away from a surface of the disk 20 during the parking operation, i.e., the parking ramp exerts a normal force on the lift tab 47 having a component Fr perpendicular to the surface of the disk 20. On the other hand, a suction force Fa, which is the resultant force of the negative pressure arising on the air bearing surface of a slider 49, acts on the slider 49 as the lift tab 47 is moved away from the surface of the disk 20 in the direction of the component Fr. The suction force forces the slider 49 towards the surface of the disk 20. Thus, the bracket 43 is flexed away from the load beam 41 to such an extent that the bracket 43 is separated from the dimple 45 of the load beam 41. Initially, though, the slider 49 may be prevented from contacting the surface of the disk 20 by the stopper 50.
However, the above-described conditions cause the bracket 43 to vibrate in a direction normal to the surface of the disk 20 (Z direction). The slider 49 is likely to collide with the surface of the disk 20 if the slider 49 continues to vibrate or pitches in a direction θ about the dimple 45. The stopper 50 can prevent the slider 49 from being displaced beyond a preset distance from the dimple 45 but cannot control the movement of the slider 49 itself. Accordingly, the conventional suspension assembly can not always prevent the read/write head from colliding with the surface of the disk 20 during the unloading process and thereby permanently damaging the disk drive or destroying the data recorded on the disk 20.
Also, the actuator can be rotated at a relatively low angular velocity during the unloading operation to minimize the vibrations of the slider 49. However, in this case, the relatively long time required for the unloading operation creates other problems for the suspension assembly and HDD.